Learn Finnish: Me haastamme itsemme tänään. - We challenge ourselves today.

Just like English uses "ourselves" instead of just "self", Finnish adds a possessive suffix to the reflexive word itse. Because the subject is me (we), we attach the first-person plural suffix -mme to make itsemme.

Why do both haastamme and itsemme end with -mme?

They both refer back to "we", but for different grammatical reasons! On the verb haastaa (to challenge), -mme is the personal ending for "we". On the pronoun itse, -mme is the possessive suffix for "our". Seeing them match is a great way to check your work.

Is itsemme acting as the object of the sentence?

Yes! We are the ones being challenged, so itsemme is the object. Normally, a total object might end in the letter -n, but Finnish has a strict rule: if a word has a possessive suffix attached to it, the object -n disappears. That is why it is just itsemme and not "itsemmen".

Can I drop the word Me from the beginning?

Absolutely. Because the verb haastamme already has the "we" ending built into it, the pronoun Me is completely optional. Saying Haastamme itsemme tänään is very natural.